Since I'm lazy I'll shamelessly copy bpat's guide structure - it's good.
The main point of this guide is to hightlight different ways to build Psyshot, which I think other guids are lacking, so let's talk about it right now.
Builds
There is only two different builds for Psyshot - build that tries to squeeze out as much damage as possible from steamgun, using mindstar for delievering melee debuffs on target/using melee buffs on himself, novice-tier.
And build, that tries to empower Psyshot's mindstar damage, using steamgun just for delivering mindstar attacks and buffs/debuffs on steamgun - advanced-tier.
There is also Nightmare, but if I wanted to utilize Nightmare I would go and play some Solipsist, it's their thing, and they are better at it, so I have no interest in this, if you want it go see bpat's guide.
Races
There are only two races that makes huge difference - Ogre and Cornac.
Ogre is for novice-tier builds and for advanced-tier too because of his Ogrewielding, Cornac is for advanced-tier none-Ogre cases - much less complicated and more reliable because of +1 cat. point on start, which makes noticable difference.
There are of cource notable Drem and Krog cases, which could make run different and easier with their miscellaneous synergy with tinker's attachments but they won't do major difference, consider them as worse-than-Cornac.
So, first the novice-tier build - you unlocked Psyshot, and want to overclock your steamgun's damage.
Stats
Dex>Str>Cun if PES or Dex>Cun>Str if going for Vital Shot, later on Dex>Cun>Str>Will.
Prodigies
It's either PES first for overall boost to your damage and steamthech talents (if you unlocked it), and then it's ICCTW! for boosting PES, or Vital Shot for good alpha-strike if you think you lack it.
Also Elemental Surge does look potent - Fire and Light elements are easy to trigger, and promise rise in damage - this is what we need.
Still not sure it's better then good old PES+ICCTW! or Vital Shot.
Category Points
Risky and rewarding approach - Avoidance>Inscription slot>Dread>Survival.
More risky and rewarding option - Avoidance>Dread>Inscription slot>Survival.
Inscription slot>Avoidance>Dread>Survival
Inscriptions
Early you will want 2 Steam Generators for your MIB, ACT and ERS, and later for Mechanical Arms, and 1 Medical Injector, second is Mind Injection which you can and should get at 12 lvl - risky since Mind Injection is a skill and can be consumed by stun, but if you are careful enough with maneuvering you can do that.
If you unlocked Inscription Slot on 20 lvl, you can get back to 2 MI.
The only reason to unlock Inscription Slot on 10 lvlt is to use some infusion/rune. I think Psyshot has enough mobility so probably some wild for debuff removal.
Later when you find good Steam Generator, you have 2 MI 1 Steam Generator and 1 infusion/rune of choce - wild for when you still don't have components for salves and resist all stacking, Primal for affinities, Heroic for being afraind of oneshots, Movement for kiting.
Tinkers
Belt: Back Support if you was struck by Str-reducing disease to keep your mobility, Fungal Web when you're using MI and need healing because swapping tinkers is instant. Sounds cheesy? Probably it is. Thunder Greanade for serious staff when you want to prevent oneshots.
Body: Spike Attachment or Armour Reinforcement early on, and then Ablative Armor only.
Cloak: Grounding Strap, various Coatings if you lack some resitances and don't care about stun.
Feet: Rocket Boots is you free Movement Infusion, Kinetic Stabiliser for Dark Crypt and escorting in Dreadfell and everywhere where you think changing position will be worse than having source of mobility. Didn't use Moss Tread so can't say anything about it.
Hands: Fatal Attractor/Toxic Canister for ranged combat, Iron Grip for when someone got close to you or you want to immobilize/reduce armor them.
Head: Headlamp for accuracy early on, Focus Lens for invisible mobs or Mental Stimulator later, Air Recycler for diving.
Lite: White Light Emitter for Crystal Edge boosting.
Ammo: Explosive Shell early on, later on only Saw Shell or Solid Shell vs single tough targets, Voltaic Shell for quick crowd clearing (10 K of summar damage without gear boosting that damage), Corrosive Shell for armor reduction, Hook Shell when you lack mobility (hypothetically).
Steamgun: Thunderclap Coating (prevents melee from getting close to you), Acid Groove (damage and armor reduction), Crystal Edge (crit multiplier and light damage).
Mindstar: Thunderclap Coating (double the chance melee won't stay close for long), Acid Groove (damage and armor reduction), Crystal Edge (crit multiplier and light damage), Silver Filigree (only if it boosts steamgun damage).
Class Categories
Psytech Gunnery: 5/1/1/1 early and core, Vacuum Shot luxury.
Psyshot is mind damage which is nice if enemy resistant to phys or fire damage. Restores psi, allows to apply melee procs on enemies - nice!
Boiling Shot is OK but nothing special, useful early for it's AoE when used with Condensate, later it's just shot with 141% weapon damage for wopping 25 steam cost.
Blunt Shot is OK early as it's AoE stun, later it's obsolete as it will be difficult to apply stun - it's steampower vs phys save and you don't have much steampower these days not sources to increase it.
Vacuum Shot has second best weapon damage modifier so you will want to for initial strike, at least one point.
Thoughts of Iron: 5/1/2/1 early, 5/1/3/1 core, 3/5 Mind Drones and 5/5 Mind Injection luxury (if you feel really generous as it only reduce cd of Frost/Water/Fiery by 1 turn).
Molten Iron Blood - you max it asap, nothing more to say about it.
Mind Drones is useful only against melee enemies in close range, and those could be actually quite lethal to you, so 3 points in it gives a nice breakpoint. Even if it will save you from one lethal strike it still worth it. Those enemies tend to be tough so you won't eliminate them fast anyway so disrupting their skills for a cost of 1 turn is good.
Psionic Mirror is simply the best mental debuff remover. Wait till enemy come close to you and gift him back all debuffs.
Mind Injection is great, use it for debuff removing and Pain Supressor Salve only and don't care about modifiers.
Mechstar: 0/0/0/0 early and core. You dont' need it. 1/1/1/0 as luxury if Steam Gens are bad and you feel you need another "go away" option for melee. Obsoleted in lategame as enemies tend to have many gap closer options so you better eliminate them than play push-and-pull game.
Gestalt: 1/0/0/0 early, 2/5/5/0 core because even weak damage shield is better then nothing, Forced Gestalt luxury.
Gestalt is what regen your psi points, it's essential. Also gives you some negligible mind/steam power boost.
Improved Gestalt is a weak damage shield with 5 turn cd (that interfere with Untouchable damage shield), but can be boosted by next skill.
Instant Channeling when maxed out and with 100 steam can seriously boost shield from Imroved Gestalt. For when your resists arn't enough and you need damage buffer for not being oneshotted. Also replenish psi which is also useful sometimes. Better have 2 Steam Generators for using it and get some steam for fight.
Forced Gestalt is only useful for enchancing your Improved Gestalt's shield, useful when dangerous enemy is in crowd, but he is not dangerous enough to oneshot you (then what's the point) or isn't in position to oneshot you. Probably useful in last fight in AoA, won't do much vs single dangerous enemy.
Action at a Distance: 1/2/0/0 early, 1/4/0/0 core, 4/4/0/0 core if Elemental Surge, otherwise 5/5 Solidify Air 4/5 Condensate and Superconduction luxury.
Condensate useful for Boiling Shot, and inflicting Wet status which halfs stun resistance - test mind saves for that. Useful early, obsolete later since you won't have mind power. Useful for clearing trash and saving your ammo (not needed past that), or essential if you aim at Elemental Surge.
Solidify Air is very good - allow you to deal damage and block enemies for 8 turns. Useful for tactical repositioning, together with Toxic Canister etc.
Superconduction reduce fire resistance which is useful for Cloack Gesture till lategame, where even debuffed like this enemies could have maxed fire resist anyway. If used on enemy with Wet status, it's AoE damage - useful for clearing trash.
Negative Biofeedback - I have no idea what to do with it. E-mail UN and call for urgent meeting of the UN Council when you know that.
Psionic Fog: 1/1/0/0 early and core, 2/5 Inhale Vapors 1/5 Psionic Fog 1/5 Uncertainty Principle luxury - if you feel that Luring is your game.
Vaporous Step is one of the best mobility skills in game. Works in vaults and places where teleports doesn't work.
Inhale Vapors is free healing on using Vaporous Step, so it's quite useful, and later worth at least second point.
Psionic Fog is another fire resistance reduced which is AoE and lasts 3 to 8 turns. Bad thing it's overwrite Superconduction debuff instead of add to it, so it's this or Superconduction. Useful for luring if you don't have Toxic Canister/Fatal Attractor.
Uncertainty Principle is bad. It can't kill you with your own projectile anymore, even at 5/5 both Psionic Fog and this you at best has 2 instance of damage avoidance. It if doesn't work against AoE then even worse.
Avoidance (locked): 5/1/3/0 early, 5/1/4/0 core, Cloak Gesture luxury.
Automated Cloak Tessellation is second half of your defence after MIB. It's not amazing but absolutely worth it - not only flat damage resistance but also deflects projectiles which could be far more useful in some situations.
Cloak Gesture is good for when you lack firepower somehow, and you need to just push a little more. Also enables ERS which is worth it alone.
Embedded Restoration Systems - imagine healing that doesn't take a turn, heals you at full hp, and have 5 turn cd. Why to imagine if ERS do all this. You only need to break LoS with enemy which is usually not hard.
Cloaking Device is for Rogue-minded persons. It's as good as stealth good in general.
Nightmare (locked) - first rule of this mini-guide is we don't talk about this.
Dread (locked): 5/0/0/0 early, 5/1/0/0 core with 5/5 Lucid Shot luxury.
Mechanical Arms does not much damage, but it debuff enemies close to you making you take less damage - and it works even when you are blind, confused, or stun or anything, continue to deal damage and debuffing. Allow to apply melee debuffs. Enable to apply Lucid Shot. Amazing thing no less.
Lucid Shot makes enemies attack other enemies, and it does work. Notable has highest weapon damage among other skills, so probably the only skill that makes sense maxing it if you feel generous.
Psy Worm is alternative psi source. Not sure it worth even 1 point.
No Hope is useless, we don't have mind power.
Generic Categories
Physics: just enough to get what you think is useful for you. Compact Steam Tank luxury - and only for charging you psionic shiled with Instant Channeling. Not as good as it can be since you don't have mind power.
Chemistry: just enough to get what you think is useful for you, Steam Power 5/5 - boosts all your steamtech talents which are all tinker attachments.
Engineering: 1/1/1/5 early and core, Supercharge Tinkers luxury.
Emergency Steam Purge is for desperate people in desperate situation. Better don't let them happen than build for them.
Innovation adds 1 stat point with 1 points in it, and I belive another 1 stat point when maxed. Not generous.
Supercharge Tinkers is OK if you can afford it - it boost your Crystal Edge, your Explosive Shot, Acid Groove, and everything that can do damage.
Last Engineer Standing is foundation for your defence - it's much harder to destroy you, if enemies can't crit. Also save your character's life when got dragged under your own not-Vital Shot shot. Also adds Cunning.
Combat Training: if you have no idea what to do here you need to probably train on other classes.
Mindstar Mastery: 0/0/0/0 early and core, Psiblades luxury.
Blacksmith (locked): leave it as it is.
Survival (locked): 1/5/0/0 early and core, it doubles the efficiency of your MI and being Ogre even triples it.
Antimagic skill tree - I should mention this, right? it's so good, it's answer to everything, you are Annihilitor - go antimagic dude, it will shut down mages almost completely, you are Brawler? you are any-none magical class - go Antimagic!
This gets an Antimagic!
That gets an Antimagic!
Everything gets an Antimagic!
To the point it being ridiculos honestly. It's like grenades in Underrail - too convenient and powerful to even thouch this.
Of course of you want optimal character - go for it.
But I won't even at gunpoint.
Gameplay
Always use Pain Supressor Salve before fight to get max resists and don't go outdoor without cap when it's cold weather or you catch cold.
Seriously, Psyshot is a class build around perfect mobility, good controls and decent defence - use this or die.
The only none-obvious thing is that you relod your ammo everytime you move since Psyshot talent doesn't provide with ammo reloading like other ranged talents do.
When and if you will find two-handed steamguns such as Shotgonne, you will start to deal 10 R damage per turn, but that was prior phys.power nerf in 1.6.
I heard you can deal 10 K damage per shot with one-handers too if you build your gear solely toward phys damage, physdamage penetration and crit modifier but I doubt you can have room for protecting gear, so you pobably won't survive for long.
Anyway, it's not a trivial itemisation to fit everyting even if it's possible.
Haven't found rest of two-handers as Psyshot (as didn't played much with it) - they say Long Arm is best (though bugged), Annihilator could be even more devastating.
Advanced-tier build is second - you realized that mindstar actually outdamages your steamgun, and want to get to the bottom of this.
And the trick is simple - you hit with mindstar every time you shoot and hit the target.
Thus Tinkerer's Twinblaster is your endgame weapon as it shoots 3 times, or Shotgonne - actually it still hit single target just 3 times, and shot 5 times only if there another 2 targets near first one, that mean the only difference with Shotgonne is you will see more damage from shooting and ammo itself. Annihilator hit 5 times respectively if you are Ogre. TT is easy to find in T1 dungeons.
Races
Cornac and Ogre both - Cornac is just supergood today, especially with all the Steam Generators, MI and talent trees unlock juggling.
Leveling fast so poweful when you need it. Ogre for ultimate damage with his Ogrewielding - but for this you will need to suffer due to exp penalty and being underleveled in comparison with Cornac. Probably an achivement on itself.
Stats
Dex 20 for some accuracy and Psyshot leveling, Cun jut enough for steamtech/tinkers unlocks, then Will>Cun>Str>Dex.
Prodigies
Superpower first as you probably won't unlock PES at lvl 25, then PES.
Also consider Elemental Surge, but again I'm not sure it's as damage efficient as PES or Superpower.
Edge case - Seeds of the Black Tree, I dunno, if you build Magic instead and take Arcane Might, it could be decent, since I hit with it in EoR for 2 K+2K Tendril Eruption, both crits. Or maybe Superpower almost as good here again, then it doesn't worth the hassle.
Category Points
Risky and rewarding approach - Avoidance>Inscription slot>Dread>Survival>Inscription Slot/Fungus if Cornac.
More risky and rewarding option - Avoidance>Dread>Inscription slot>Survival>Inscription Slot/Fungus if Cornac.
Otherwise Inscription slot>Avoidance>Dread>Survival>Inscription Slot/Fungus if Cornac.
Same as before, and I dont' recommend going for Dread first - it's too risky.
Edit: you should understand that in Fungus tree you want only additional HP from Wild Growth, and nothing more. You have no problem with healing in endgame as psyshot is very durable and you oneshot rares and two-threeshot uniques and bosses, almost all of them (in normal game not including Far Portal and such). My character that won game on Insane instead - as I lacked generic points - unlocked 5th inscription slot and got Primal Infusion, Infusion of Wild Growth also be an option - 50 armor, pinning and some damage is good, as I used it on my previous char - wyrmic.
Inscriptions
2 Steam Generators for your MIB, ACT and ERS, and for Mechanical Arms later, 1 MI, second is Mind Injection at 12 lvl.
If you unlocked Inscription Slot on 20 lvl, you can get back to 2 MI.
The only reason to unlock Inscription Slot on 10 lvl is to use some infusion/rune when you haven't found Steam Gens.
Later when you find good Steam Generator, you have 2 MI 1 Steam Generator and 1 infusion/rune or 2 MI and 2 Steam Gens (which requred only for Instant Channeling charging your shield for special situations).
Edit: turned out, 2 steam generators is superiour option, as you want to have charged shield all the times in serious fight, where you can't just oneshot mob. You need that damage buffer to avoid oneshots.
Tinkers
Belt: Back Support, Fungal Web, Thunder Greanade - swap and cheese.
Body: Spike Attachment, Armour Reinforcement -> Ablative Armor only.
Cloak: Grounding Strap, Coatings.
Feet: Rocket Boots, Kinetic Stabiliser. Moss Tread could be more useful as character always close to the enemy.
Hands: Fatal Attractor/Toxic Canister, Iron Grip.
Head: Headlamp only, occasional Focus Lens , Air Recycler for swimming pool sinking.
Lite: White Light Emitter, Black Light Emitter for when you have Seeds of the Black Tree.
Ammo: Explosive Shell, Saw Shell, Solid Shell, Voltaic Shell, Hook Shell, Toxic Shell, Botanic Shell - why am I even listing all of them? Just try them out.
Steamgun: Thunderclap Coating (only when melee mobs right near you), Acid Groove (only early for damage), Crystal Edge.
Mindstar: Thunderclap Coating (double the chance melee won't stay close for long), Acid Groove (when you haven't found Razor Edge), Razor Edge if your crit chance for mindstar less then 100%, if 100 then Crystal Edge, Silver Filigree for edge cases.
Class Categories
Psytech Gunnery: 5/0/0/0 early and core, 5/4/0/0 if going to use Core of the Forge/Elemental Surge, otherwise Boiling Shot luxury.
Psyshot is your main source of damage - just look at these sweet 275% of mindstar damage. Yes, it doesn't work with Psiblades, because if it would, Psyshot would just turned into another Arcan Blade.
Steamgun here is just to deliver your mindstar sttacks, for Mana Clash and other such debuffs if you for some reason don't want to use TT.
With TT you have triple chance to trigger all procs, quadruple with Mechanical Hands.
All the procs you need are simply quadrupled vs doubled with usual steamgun.
Also I did once build that doesn't use steamgun at all - just 2 mindstars and Mechanical Hands which do work with Psiblades.
Guess it could be even more viable now.
Boiling Shot is only for fire-themed build or Elemental Surge procs.
Blunt Shot only useful early, floating points or don't bother as you will have another options.
Vacuum Shot is a history, use it only if for some reason want it's pulling mechanic.
Thoughts of Iron 5/1/2/1 early, 5/1/3/1 core, 3/5 Mind Drones and 5/5 Mind Injection luxury.
Just as before - nothing changes.
Mechstar: 0/0/0/0 early and core. You have better options early on, and later you will oneshot everything. 1/1/1/0 as luxury.
Edit: Thanks to Kuroto, richardhawk and Snarvid guide acknowledged the fact that Vital Shot isn't №1 self-killer like it used to be, now it pass safely through your flimsy body. Also other things, Compact Steam Tanks suggestion from Dajawn's guide.
Gestalt: 1/0/0/0 early, 2/5/5/0 core because even weak damage shield is better then nothing, Forced Gestalt luxury.
Same as before, except it's noticeable better now and this is what you need against ridiculous oneshots.
Edit: turned out Forced Gestalt was the least useful. In theory it was a buff for mind power, to successfuly land No Hope.
In reality, nobody ever resisted No Hope at Far East and at High Peak, last fight included. It has more use as defensive move, also it's still doubtful as it spend a turn. Still could be useful as it weakens enemy's attack for 5 turns.
Action at a Distance: 1/2/0/0 early, 1/4/0/0 core, 5/4/0/0 core if Elemental Surge or fire-themed build using Core of the Forge, otherwise 5/5 Solidify Air 4/5 Condensate and Superconduction luxury.
Condensate is more useful as Wet status will stick much more often, though still useless for Blunt Shot. If Thunder Greanade work different then Blunt Shot - yay! it's useful!
Condensate, Solidify Air and Superconduction are enablers for Elemental Surge or if you built fire-themed Psychot, Superconduction for lowering fire resisance in that case.
Psionic Fog: 1/2/0/0 early and core, 5/2/5/0 core if fire-themed build or Elemental Surge, otherwise 1/5 Psionic Fog, 1/5 Uncertainty Principle luxury,
Edit: in endgame with just 2 points in Inhale Vapours char got 600+ hp with crit heal, without charging it.
Avoidance (locked): 5/1/3/0 early, 5/1/4/0 core, 5/5/4/0 core if Elemental Surge or fire-themed build, otherwise Cloak Gesture luxury.
Edit:Actually I think, this is where 5 points from Forced Gestalt should be - stealth power would be enough to fool anyone even at High Peak. Try it out.
Dread (locked): 5/0/0/0 early and core with 5/1/1/2 No Hope luxury.
Mechanical Arms is much more powerful skill now. With not-TT steamgun it deal a ~third of your overall damage.
We have mindpower, but is it enough for No Hope to work? Still worth to try it out.
Edit: turned out yes, you have enough mind power, 106 without PES, 118 with PES.
Edit: I went with 5/1/1/3 and it was fine all the way downt to... Atamathon, and there was when I felt that a bit lacking duration for No Hope. If you want to be more comfortable with Atamathone - max No Hope/
Generic Categories
Physics: what yout heart desires - and few points in Compact Steam Tank if possible, since it has better return for Instant Channeling with higher mind power.
Edit: Oh yeah! in endgame shield crit for 1700 hp with 250% critmult. Well worth spending 5 points there.
Chemistry: same, 5/5 in Steampower if you ever want your tinkers will work.
Engineering: 1/1/1/5 early and core, Supercharge Tinkers and according to Dajawn 2/5 Innovation luxury.
Combat Training same, 5/5 Thick Skin 3/5 Heavy Armor Training, 5/5 if you really desperate.
Mindstar Mastery: 5/0/0/0 early and core - max it asap, bear in mind escorts.
Psiblades (as skill) still boosts mindstar damage and gives some phys power - unprecedented generosity!
Survival (locked): 1/5/0/0 early and core. Not as efficient as for Ogre, but efficient enough.
Antimagic: resist the urge! while it makes much more sense to go Antimagic for this character, still no.
For those who still want some rundown - 1/1/1/1 if you can, or 3/1/1/1 if you can, or if you want to abslolutely secure your char - add as many points in Mana Clash till the game will explode from your awesomness.
Fungus (locked) For Cornac, if you went Antimagic and weird in same time you can also get Fungus, to free your injectors from healing and to get healing when your injectors on cd, and get larger hp pool, the problem is category points that are running out.
Gameplay
Early on till lvl 25, maybe 30 you will oneshot almost anything (with t4-t5 mindstar), at worst two-shot. Since the only none-artefact mindstar damage is Nature - build your gear appropriately. Or not - I have no bonus Nature damage gear except Spellhunt Remnants lvl 3 and still eliminate threats before they could do anything to me.
You could theme your build around artifact mindstars - when and if you'll find them haha - though only lvl 4-5 of these worth using.
Seeds of the Black Tree is amazing trash cleaner - Tendril Eruption hits for 2 K? Without Superpower? Yes please.
Eye of the Wyrm, Oozing Heart, Nexus of the Way, Amethyst of Sanctuary, Core of the Forge, Eyal's Will - they could probably offer something to a player.
Also not sure, I saw in action only SotBT and NotW.
If no - I heard randart mindstars could be even more powerful.
As for Ogre - you need to just find
Shotgonne or Annihilator, and get +1 and +2 mindstar hits.Though good luck with that.
For those who want to ambush me, saying that Tinkerer's Twinblaster is as broken as Sawrd - bite it, it's still in game and I'll agree with this only when it vanishes. And then there still will be Shotgonne and Annihilator.
P.S. I honestly have only vague idea about itemisation as I'm playing this mindstar-oriented Psyshot right now. So of course add your suggestions, feel free to criticize anything.
Edit thanks to Kuroto, richardhawk and Snarvid guide acknowledged the fact that Vital Shot isn't first self-killer anymore, also about existance of Elemental Surge.
Edit2 - clarified Shotgonne machanics, notes on category points unlock, inscriptions, Gestalt, Psionic Fog, Avoidance, Dread, Physics, grammar..
Edit 3 - Dread.
Edit 4 - more logical formatting, grammar.
Soon. Also it's guide for 1.6, where it's even more reasons to use mindstar for damage.
